Seawater and factory wastewater have a bad influence on the human body because they include large amounts of heavy metals and organic or inorganic pollutants. In addition, environmental pollution problems are getting worse due to various harmful materials caused by recent development of industrial fields and high growth, and thus, an agent for treating the harmful materials is required to be developed.
A chelate ion-exchange resin, an activated carbon, an acrylamide polymer fiber, etc., are widely used for adsorption of metal ions from an aqueous solution. Among these methods, the chelating method is mainly used in separation and concentration systems.
Among strategic rare metals (lithium, cobalt, molybdenum, manganese, tungsten, titanium, magnesium, indium, rare earth, chromium and nickel) that are of interest as a part of securing resources by the government currently, nickel is widely and mainly used for manufacturing secondary batteries and special steels, and it is an important rare metal that has received attention as a metal that is absolutely necessary for Korea's core industries at present. However, the nickel is mostly and currently imported in Korea.
Therefore, it is significantly important to separate and concentrate nickel as a high-value-added resource in consideration of the fact that Korea lacks natural resources. Nanoporous silica materials having high surface area and nano pores are potential candidates for the separation and concentration of nickel.
The nanoporous silica materials are generally synthesized using a monomolecular surfactant or a polymer material having hydrophilic and hydrophobic moieties as a template, and using an inorganic material based on silica as a pore wall forming material, through a self-assembly phenomenon in an aqueous solution. The nanoporous silica material began to be synthesized for the first time in 1992 by Beck and co-researchers (Beck, J. S.; Vartuli, C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T-W.; Olson, D. H.; Sheppard, E. W.; McCullen, S. B.; Higgins, J. B.; Schlenker, J. L. J. Am. Chem. Soc., 1992a, 114, 10834, and Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J. S. Nature, 1992, 359, 710), and many studies have been conducted.
In addition, the nanoporous silica material has many silanol groups (Si—OH) present on surfaces of pores. Therefore, alkoxysilane having an organic functional group may be modified through a chemical reaction. These modified nanoporous silica materials have regular pore arrangements, uniform pore size, and high surface area, thereby selectively adsorbing macromolecules, enzymes, and metal ions to have significantly high applicability to specific catalytic reactions, sensors, drug delivery, and production of nanomaterials, etc. Meanwhile, nanoporous silica materials without pore surface modification exhibit poor selectivity to the above-described macromolecules, enzymes and metal ions, and exhibit low adsorptivity.
Therefore, the present inventors found that when a pore surface of the nanoporous silica material was modified with a functionalized silane compound, an organic ligand having high selectivity to metal ions was incorporated in pores, and then, the functionalized silane compound was collected using a cyclic molecule, and thus, an organic-inorganic hybrid nanoporous silica material having a closed pore form could be synthesized, and the metal ions could be adsorbed and separated with high selectivity from seawater or wastewater by using this organic-inorganic hybrid nanoporous silica material, and completed the present invention.